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RE: Gaps between plywood sheathing

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In addition,  the APA publication of 1998 Residential & Commercial
Design/Construction Guide is very specific that the gaps are required.  As
far as testing goes,  APA 158,  specifically states that the panels tested
have the 1/8" gap.  While some of the other Reports 138 and 157 don't
specifically state the 1/8" gap, but the (few close up) pictures seem to
show it.

Another gap to mention would be at the Rim joist.  ATC7 recommends placing a
1/2" gap at the center of the RIM to allow for shrinkage of sawn lumber.

I also have seen OSB buckled 4" off the studs at the middle where the
sheathing had not been properly gapped, immediately adjacent to sheets which
had been gapped and were just fine.  Carpenters who care,  and there are
many,  use a nail to gap the sheathing.

All of the shop drawings I used review for panelized roofs had the purlin
and girder spacing adjusted for plywood gaps.  No Exceptions Taken, as the
stamp says.  However,  it has been about 10 years since I have seen a shop
drawing for panelized roofs,  are companies like Bevon-Heron (So. Cal) even
still doing these types of shop drawings ?


Robert Shaffer, PE
Santa Cruz,  CA



-----Original Message-----
From: Neil Moore [mailto:nmoore(--nospam--at)innercite.com]
Sent: Thursday, April 19, 2001 7:20 AM
To: seaint(--nospam--at)seaint.org; seaint(--nospam--at)seaint.org
Subject: RE: Gaps between plywood sheathing


Dennis:

I just grabbed the first APA publication in my timber file drawer, which is
the APA Product Guide for Performance Rated Panels.  This publication is a
January 1986 issue:

Under Panel Size and Spacing:

"Recommended spacings between panels are 1/8 inch at end joints and 1/4
inch at edge joints for APA RATED SHEATHING and 1/8 inch at both ends and
edges for APA RATED STURD-I-FLOOR, unless otherwise recommended by the
manufacturer."  (Capitol letters are as published. )

I know that my firm went through all the causes of the buckling problems
that we encountered in installed sheathing.

Neil Moore, S.E.
neil moore and associates



At 09:40 PM 4/18/2001 -0700, Structuralist wrote:
>While others are agreeing with the 1/8" spacing for plywood, I've only read
>the standard for OSB which requires the gap. I don't recall anything in the
>APA documents either on leaving expansion joints for plywood panels.
>Dennis
>
>> -----Original Message-----
>> From: George Richards, P.E. [mailto:george(--nospam--at)BORM.com]
>> Sent: Wednesday, April 18, 2001 3:46 PM
>> To: 'seaint(--nospam--at)seaint.org'
>> Subject: RE: Gaps between plywood sheathing
>>
>>
>> The numbers do not add up and I have never seen anything in APA lit. to
>> address this issue.  Engineering Judgment.
>>
>> George Richards, P. E.
>>
>> -----Original Message-----
>> From: Michael Bryson [mailto:michael.bryson(--nospam--at)englekirk.com]
>> Sent: Wednesday, April 18, 2001 1:27 PM
>> To: seaint(--nospam--at)seaint.org
>> Subject: Gaps between plywood sheathing
>>
>>
>> Typically you install sheathing with a 1/8" gap between sheets to
>> allow for
>> some expansion, correct? If the sheets are supported by a 2x
>> framing member,
>> how do you get your edge distance for a 10d nail?
>>



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